The present invention relates to a cassette loading mechanism for a recording/reproducing apparatus and, more particularly, to a cassette insertion stabilizing apparatus and an incorrect cassette insertion preventing apparatus for ensuring successful insertion of two kinds of tape cassettes, i.e., a smaller tape cassette and a larger tape cassette differing from each other in case size and thickness, through a cassette inlet opening formed in a recording/reproducing apparatus to set either the larger tape cassette or the smaller tape cassette at a predetermined position within the recording/reproducing apparatus.
SML cassettes having different case sizes corresponding to recording times, such as D3 cassettes, are well known. Such cassettes are described in the "Proposed SMPTE Standard for Digital Video Recording 1/2 inch Type D3 Composite Format Tape Cassette", Jan. 2, 1992. A cassette loading mechanism capable of correctly loading such tape cassettes of different sizes is disclosed, for example, in Japanese Utility Model Publication (Kokoku) No. 5-16672.
As shown in FIG. 6A, the D3 cassette has a locking member 5 for locking a front lid 3 at a closed position, and the locking member 5 is supported pivotally on the side wall of the case body of the cassette. When the cassette is inserted in a cassette holder 11 in the direction of the arrow A, an unlocking member 7 engages the locking member 5 and turns the locking member 5 in the direction of the arrow B to unlock the front lid 3. A lengthwise guide groove 100 is formed in the bottom wall of the case body and a guide rail 12 is formed on the cassette holder 11. When the cassette is inserted in the cassette holder 11, the guide rail 12 engages the guide groove 100 to guide the cassette to prevent the incorrect insertion of the cassette. Therefore, a plurality of cuts of a depth L are formed in the lower part of the front wall of the D3 cassette. When the cassette is inserted in the cassette holder 11 in the direction of the arrow A, a stopper 22 engages a stepped part 8 formed in a fixed part of the front lid of the cassette to position the cassette on the cassette holder 11.
An 8 mm video tape cassette as shown in FIG. 6B has a construction similar to that of the D3 cassette. The 8 mm video tape cassette differs from the D3 cassette in that the front lid 3 of the 8 mm video tape cassette does not have a part corresponding to the stepped part 8.
Recently, further reduction in size and weight of recording/reproducing apparatus (VTR), such as video cameras, has been desired and efforts for the development of techniques for the reduction in size and weight of recording/reproducing apparatus have been made in other fields as well. Generally, the size of a VTR mechanism is dependent on the respective shapes of the cylinder and the cassette. Therefore, the sizes of the cylinder and the cassette must be reduced to reduce the size of the mechanism. Efforts for increasing the rotating speed of the cylinder and the contact angle have been made to reduce the diameter of the cylinder, and efforts have been made to develop a new cassette of external dimensions smaller than those of the 8 mm video tape cassette.
If the thickness of such a new cassette is reduced to its smallest possible thickness, it becomes impossible to form a guide groove corresponding to the guide groove 100 in the cassette for preventing the incorrect insertion of the cassette in the bottom wall of the new cassette. Also, any stepped part like the stepped part 8 of the 8 mm video tape cassette as shown in FIG. 6B is not formed in the front wall of the new cassette having a very small thickness. A system intended to use the foregoing plurality of cassettes differing from each other in size and shape must be provided with means for correctly receiving any one of those cassettes without using the guide groove system. If the cassettes are not provided with the stepped part 8, the system must be provided with means for ensuring stable operation without forming any guide groove for avoiding interference with the lid unlocking members disposed at different positions used for the different sizes of the cassettes.
A larger cassette and a smaller cassette based on the current 8 mm video tape cassette, and a cassette holder for holding such cassettes will be described with reference to FIGS. 7A and 7B.
Referring to FIGS. 7A and 7B, there are shown a smaller cassette 1, i.e., a cassette having comparatively small external dimensions for holding an 8 mm video tape, a larger cassette 2, i.e., a cassette having comparatively large external dimensions for holding an 8 mm video tape, a cassette holder 11, guide members 12a and 12b fixed to the cassette holder 11 at an interval slightly greater than the width W of the smaller cassette, a first lid unlocking member 7 for unlocking the lid of the smaller cassette, first insertion limiting members 22 for limiting the insertion of the smaller cassette in the cassette holder 11, a second lid unlocking member 18 for unlocking the front lid of the larger cassette, and second insertion limiting members 17. The first insertion limiting members 22 and the second insertion limiting members 17 are provided respectively for the smaller cassette and the larger cassette, because the opening 101 of the smaller cassette and the opening 102 of the larger cassette are different from each other.
When the smaller cassette having a reduced thickness and the larger cassette are formed on the basis of the 8 mm video tape cassette, the cassette holder 11 must be provided with the guide members 12a and 12b specially for the smaller cassette, and with lid unlocking members and the insertion limiting members respectively for the smaller cassette and the larger cassette. When inserting the larger cassette 2 in the cassette holder 11, the guide members 12a and 12b for guiding the smaller cassette, the first lid unlocking member 7 and/or the first insertion limiting members 22 interfere with the larger cassette 2. Consequently, in the conventional apparatus the larger cassette 2 cannot be set in place in the cassette holder 11.